Manufacture of alkali-nitrogen fertilizers having urea as their base



Patented Feb, 22, 1927.

UNITED STATES Y 1,616,266 PATENT OFFICE.

JOSEPH BRESLAUER, OF GENEVA, SWITZERLAND, ASSIGNOR T COMPAGNIE DE LAZOTE ET DES FERTILISANTS S. 11., 0F GENEV A, SWITZERLAND, A SWISS COM- MANUFACTURE OF ALKALI-NITROGEN FERTILIZERS'HAVING UREA AS THEIR BASE.

No Drawing. Application filed June 22, 1925, Serial No. 38,917, and in Switzerland June 26, 1924..

This invention relates to the manufacture from calcium 'cyanamide, of alkali nitrogen fertilizers having urea for their-base.

Heretofore acids and acid catalyzers have 'been' utilized forthe preparation of cyanamide and itsconversion into urea, in order to obviate the pol merization'of the cyanamide, into the mj'urious dicyandiamide,

for example, when working in an alkaline medium.

Moreover according to the work of Kruger and Grube, the polymerization of the cyanamide, for example, into dicyandiamide,

reaches its maximum for a given concentration of the h droxyl ions and then diminishes rapidly as t e amount of hydroxyl ions in creases. j

According to the process forming the subject" of this invention, alkali nitrogen fertilizers are madeby converting the cyanamide into urea by caustic alkalis produced by double decomposition from salts of alkali 'metals wi h the free lime of the calcium cyanamide. v

This double decomposition gives very strong bases which permit ofworking under conditions which-are unfavourable for the polymerization of the cyanamide.

In order to carry this process into pracg0 tice either salts of potassium or salts ofsodium can be used, In the example given be: low, there are used, for example, salts of potassium such as, for example the sulphate of ot-assium, and there is obtained a mixed ertilizer containing in addition to urea, more especially carbonate of potassium.

The. operation is as follows: i To a saturated solution of sulphate of potassium for example, there is added at temo peratiires between and 120 degrees C. in small uantities raw commercial calcium cyananude, the amount of which being reckoned so that the free lime of the calcium cyanamidecorres onds in the maximum case 5 to the acid ra ical of-.th e sulphate of po-.

tassium. When all the cyanamide is introduced, the mixture is stirred during about a quarter of an hour and in order to separate the sulphate of lime formed, the soluio tion is filtered. This solution, which contains caustic potash in, addition to the potassium cyanamide, is then brought to the boiling point or to a higher temperature, for ex ample, in an autoclave, in order to effect the plete conversion into urea, the solution can be treated in this manner directly afterfiltration; the solution thus" obtained is then used to precipitate the lime of a fresh quantity of calcium cyanamide and becomes enriched in nitrogen.

The heating of the alkaline solution, can also be efi'ected for example before the filtration, such heating being continued until the complete conversion of the cyanamide into urea is effected. obtained directly.

which is very rich in fertilizing materials and has the advantage that the proportion of nitrogen relatively to the carbonate of potassium may be varied as desired within certain limits.-

It will be understood that solutions consistmg very largely or primarily of normal salts are to be used, and that the presence of acid salts suflicient to materially lessen or delay the attainment of the required hydroxyl ion concentration is to be avoided.

\ We claim:

1. A. process of conVertingcalcium cyanamid into urea which comprises, forming an alkaline solution of cyanamid by adding the calcium cyanamid to a solution of an alkali metal normal salt, and heating the resulting alkaline solutionof cyanamid to form urea.

2. A processof converting calcium cyanamid into urea which comprises, forming an alkaline solution of cyanamid by the addition of the calcium cyanamid to a solution of al potassium normal salt, and heating the resulting alkaline solution of cyanamid to form urea.

3. A process of converting calcium cyan- The mixed fertilizer is thus The resultant product forms a fertilizer amid into urea which comprises, forming an I alkaline solution of cyanamid by adding calcium cyanamid to a potassium sulphate solution, and heating the resulting solution of cyanamidand alkali to form urea.

4. A process of converting calcium cyanamid into urea which comprises, forming an alkaline solution of cyanamid by adding ca!- cium cyanamid to' a solution of an alkali metal normal salt, heatin the resulting alkaline solution of cyanami to form urea, and new tralizing the alkali with carbon'dioxide.

5. A process of converting calcium cyanamidinto urea which comprises, forming an alkaline solution of cyanamid by adding calcium cyanamid to a solution of a normal 0- tassium salt of an acid forming an'insolu ile com ound with calcium, removing the insolu le calcium compound, neutralizing the resulting alkaline solution with carbon diaside, and adding calcium cyanamid to the resulting solution of alkali carbonate and cyanamid, and bringing said solution to a tem erature sufiicient tq convert the cyanami to urea.

6; A process of converting calcium cyanamid into urea which comprises, forming an alkaline solution of ,cyanamid by adding calcium cyanamid to a solution of potassium sulphate, the maximum quantity of calcium cyanamid being equivalent to the sulphate radical of the potassium sulphate, and heating the resulting solution to change the eyanamid to urea. v

7 A process of converting calcium cyanamid into men which comprisesfadding calcium cyanamid to a solution of an alkali metal normal salt at a temperature between 302 C. and 120 C. to form an alkalinesolution, heating the resulting alkaline solution of cyanamid at a boiling temperature or higher to change the cyanamid to urea, and neutralizing the resulting alkaline solution of cyanamid to urea. in A process of converting calcium cyanamid into urea which comprises forming an alkaline solution of cyanamid by adding calmetal normal saltof an acid forming an insoluble compound with calcium, removing the insoluble calcium compound, neutralizmg the resulting alkaline solution of cyanamid with carbon dioxide, addingadditional calcium cyanamld to the resulting solution.

JOSEPH BRESLAUER.

ciunn cyanamid to a solution of an alkali 

